A Formally Zwitterionic Ruthenium Catalyst Precursor for the Transfer Hydrogenation of Ketones that Does Not Feature an Ancillary Ligand NH Functionality

Fast and furious: Even without the assistance of an NH donor ligand, the Ru complex shown in the scheme is a remarkably active precatalyst for the transfer hydrogenation of ketones in basic iPrOH (R,R′=alkyl or aryl), providing near-quantitative yields within minutes and exhibiting consistently high turnover frequencies (104 to 105 h−1) for a diverse range of substrates.